A security update for Apple’s iPhone does more than just fix critical flaws in the handset. It also looks for and wipes out any modifications that users make to the firmware on their phones, according to hackers looking to unlock the phone.

But the security update does not break any of the tools that hackers have so far developed to modify the iPhone’s firmware, they said. The iPhone v1.0.1 update primarily addresses a security flaw uncovered in the handset’s Safari browser that was to be detailed Thursday at the Black Hat 2007 conference in Las Vegas.